Determination of the solid–water distribution coefficient ( Kd) for pharmaceuticals, estrogens and musk fragrances in digested sludge

Abstract

This work determined the solid–water distribution coefficient ( K d) and the organic carbon normalized distribution coefficient ( K oc) of several pharmaceuticals (carbamazepine, ibuprofen, naproxen, diclofenac, iopromide, sulfamethoxazole and roxithromycin), three estrogens (estrone, 17 β-estradiol and 17 α-ethinylestradiol) and two musk fragrances (HHCB and AHTN) in digested sludge. These sorption coefficients can be used to evaluate the fate of these substances during sludge treatment, thus avoiding the expensive and time-consuming analysis in the sludge phase. For determining the K d and K oc values of the target compounds in digested sludge, their concentrations were measured in the aqueous and solid phase of the effluent of an anaerobic digestion pilot plant run at several operational conditions. The results obtained were compared with the values modelled by using simple K ow approaches. The resulting log K d values ranged between 3.5 and 4.4 for the two musk fragrances (log K oc of 4.5–6.0), between 2.1 and 2.9 for estrogens (log K oc of 2.9–4.2) and between 0.8 and 1.9 for the remaining pharmaceuticals (log K oc of 1.8–3.5). These values are in the same range as those reported in the literature for primary and secondary sludge and no significant influence of the anaerobic digestion operational conditions was observed. For most compounds, the modelled K oc were close or within the lower range of the experimentally determined K oc. Major deviations of the modelled K oc values were found for iopromide, sulfamethoxazole and roxithromycin, which were 1–3 orders of magnitude lower than the measured values.